1. Field of the Invention
The present invention relates to congestion control method and system in an exchange.
2. Description of the Related Art
FIG. 15 shows a normal status in case that is accommodated in a general exchange 1. As shown in FIG. 15, in this case, the calling subscriber can talk with a desired subscriber if a trunk 3 on an output side of the exchange 1 is idle and the desired subscriber is not talking.
FIG. 16 shows a busy or congested status in the above-described case. If the trunk 3 is not idle because of call congestion, or a desired subscriber's phone is busy, as shown in FIG. 16, a congestion tone (CT) or busy tone (BT) is transmitted to the calling subscriber, and then, the calling subscriber can hear the tone.
In here, a flow chart for connecting a BT/CT is shown in FIG. 17. As shown in FIG. 17, if a calling is incoming (STEP S2) when a trunk 3 is in an idle status (STEP S1), an exchange 1 receives a telephone number of the calling subscriber (STEP S3). Then, the exchange 1 judges whether or not there is an idle trunk 3 on its output side (STEP S4).
If there is an idle trunk 3, channel connection can be performed. If not, the exchange 1 connects with a BT/CT transmitter 4 to send a congestion tone (CT) or busy tone (BT) to the calling subscriber.
In here, call congestion may be caused by that many subscribers try to send callings at the same time, and as shown in FIG. 18, repeat hanging and calling without waiting after they hear a congestion tone or busy tone (BT). Therefore, this situation makes the call congestion status be aggravated more, thus it becomes hard to connect with a desired subscriber.
It is a matter of frequent occurrence to experience a similar situation such that it becomes hard to connect to a specific line because many subscribers concurrently call one line up, especially in an emergency. The reason is because most of the subscribers repeat the above-described situation of FIG. 18.
In such a situation, a congestion can be relieved by controlling the incoming to enable connection in order to solve the above-described problem till now. In the conventional method, a subscriber can not be connected to a specific channel, temporarily, and the specific channel is compulsorily made to an idle status to prevent from congestion.
However, in this method, congestion occurs again right away, in other words, a vicious cycle is repeated. Thereby, a quality of call connection service becomes lower. This means the conventional method is not preferable.